Step 1: What black dots?

The black dots you see don't really exist. Whenever you try and look at one directly, it will disappear. I don't know why this happens as I haven't found a good explanation for it. Feel free to let me know if you have any insight into the comments.

The goal of this Instructable is to show you how to quickly recreate such a grid with a graphics program. You can then make some variations of your own.

To start with we'll want a gray background. Lock this or put it on another layer and then start making your building block.

Step 2: Building block, pt. 1

We want to have a clean grid so that we're not distracted from the illusion by an uneven pattern.

To start, make a black square and make two identical smaller squares of another color. Attach these squares to the right and bottom of the black square.

These smaller squares will determine how wide the lines between the black squares are and are a guide for all the copying we'll be doing.

Now group the squares and let's go.

Step 3: Copy and paste

Copy the group and paste it directly to the right of the original group so that the small square just touches both black squares.

Now select all of the squares, copy them, and paste them directly below the first group. Use the little squares as a guide again to keep the distance consistent.

The results should look like the image below.

Step 4: Add a white circle

Create a white circle that fits right inside the intersection of the four black squares. This will take a bit of fidgeting to get the size and placement right, but make sure it fits well.

Step 5: Finish the building block

Delete everything but the original three squares and the white circle. You have now finished making the basic building block of this grid.

"In neurobiology, lateral inhibition is the capacity of an excited neuron to reduce the activity of its neighbors. Lateral inhibition disables the spreading of action potentials from excited neurons to neighboring neurons in the lateral direction." this is happening in your eye..

It's pretty complicated to explain. I'm a psych PHD, and I don't entirely understand it, even after reading a lot just now and having taken perception courses (I don't do vision stuff at all, though, of course). Basically, all of the theories out there right now have one thing in common, though - they all agree that this is an illusion caused by one or more of various systems our nervous system uses to try and detect edges better. Edges are immensely important to people, because they help us perceive the shape of an object, and the boundaries of an object, so we have evolved a visual system that is not only good at seeing them, but actually goes out of its way to make the edges MORE visible than they are in real life. This enhancement goes too far, sometimes, though, causing us to see false edges, like in the illusion. Then it's downhill from there in terms of details. I always learned it was opponent cells, but meh.

I dont see the red/green one, probably my bad eye.I tryed to make a gradient version, you clearly see the dot are darker on top.I also tryed to put another image in the square, also seem to work.I also noticed that the smaller the grid is, the better you see the dot. for exemple, make a really huge version and you barely see the dot.

If I focus my eyes exclusively on one of the small squares in the grid, I do not see a black dot. So in my mind it is when we look at the entire grid that we see the black dots (if grid squares are red we see red dots etc.). Good optical illusion!